Multi-phase voltage regulator control

ABSTRACT

A control system for a multi-phase power system includes a first phase line, a second phase line, and a third phase line. The control system includes a plurality of regulator controls including a first regulator control configured to control a first tap changer associated with the first phase line, a second regulator control configured to control a second tap changer associated with the second phase line, a third regulator control configured to control a third tap changer associated with the third phase line, and an electronic processor coupled to the first regulator control, the second regulator control, and the third regulator control. The electronic processor is configured to regulate the voltage of the multi-phase system using the first, second, and third regulator controls.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/893,717, filed on Aug. 23, 2022, which claims the benefit of U.S.Provisional Patent Application No. 63/236,080, filed Aug. 23, 2021, U.S.Provisional Patent Application No. 63/241,294, filed Sep. 7, 2021, andU.S. Provisional Patent Application No. 63/251,342 filed Oct. 1, 2021,the entire contents of which are hereby incorporated by reference.

FIELD

Embodiments relate to multi-phase voltage regulators and controlthereof.

SUMMARY

One aspect of the present disclosure is directed to a multi-phasevoltage regulator controller implemented using voltage regulatorcontrols that are electrically connected to a single printed circuitboard for controlling various aspects of each phase of a multi-phasevoltage regulator.

In one aspect, a control system for a multi-phase power system includesa first phase line, a second phase line, and a third phase line. Thecontrol system includes a plurality of regulator controls including afirst regulator control configured to control a first tap changerassociated with the first phase line, a second regulator controlconfigured to control a second tap changer associated with the secondphase line, a third regulator control configured to control a third tapchanger associated with the third phase line, a converter circuitconfigured to convert power flowing through the first, second, and thirdphase lines to levels used for powering the first, second, and third tapchangers and an electronic processor coupled to the first regulatorcontrol, the second regulator control, and the third regulator control.The electronic processor is configured to determine whether a voltagelevel of the first phase line exceeds a threshold, control a first relayto power the first tap changer with power converted from the first phaseline to effect a tap change on the first phase line when the voltagelevel of the first phase exceeds the threshold, determine whether avoltage level of the second phase line exceeds the threshold when thevoltage level of the first phase line is less than the threshold, andcontrol a second relay to power the first tap changer with powerconverted from the second phase line to effect a tap change on the firstphase line when the voltage of the first phase line is less than thethreshold.

In another aspect, a control system for a multi-phase power systemincludes a first phase line, a second phase line, and a third phaseline. The control system includes a plurality of regulator controlsincluding a first regulator control configured to control a first tapchanger associated with the first phase line, a second regulator controlconfigured to control a second tap changer associated with the secondphase line, a third regulator control configured to control a third tapchanger associated with the third phase line, and an electronicprocessor coupled to the first regulator control, the second regulatorcontrol, and the third regulator control. The electronic processor isconfigured to determine an average voltage of the multi-phase powersystem based on a voltage of the first phase line, a voltage of thesecond phase line and voltage of the first phase line, determine avoltage regulation command based on the average voltage and amulti-phase setpoint, determine whether the first tap changer, thesecond tap changer, and the third tap changer are set to a same tapposition, issue the voltage regulation command to each of the first,second, and third regulator controls when the first tap changer, thesecond tap changer, and the third tap changer are at the same tapposition.

In another aspect, a control system for a multi-phase power systemincludes a first phase line, a second phase line, and a third phaseline. The control system includes a plurality of regulator controlsincluding a first regulator control configured to control a first tapchanger associated with the first phase line, a second regulator controlconfigured to control a second tap changer associated with the secondphase line, a third regulator control configured to control a third tapchanger associated with the third phase line, and an electronicprocessor coupled to the first regulator control, the second regulatorcontrol, and the third regulator control. The electronic processor isconfigured to determine whether each of a voltage of the first phaseline, a voltage of the second phase line, and a voltage of the thirdphase line are within band of a target bandcenter, perform a voltageregulation operation when one or more of the voltages of the first phaseline, the second phase line, and the third phase line are out of band ofthe target bandcenter, determine whether any of the voltages of thefirst phase line, the second phase line, and the third phase line differfrom the target bandcenter by more than a threshold, and adjust a tapposition of the tap changer associated with the phase line having avoltage furthest from the bandcenter when any of the voltages of thefirst phase line, the second phase line, and the third phase line differfrom the target bandcenter by more than the threshold.

Other aspects of the disclosure will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate a controller for a voltage regulator tap changingsystem according to various embodiments.

FIG. 2 illustrates a printed circuit board included in the controller ofFIGS. 1A-1C

FIG. 3 is a block diagram of a control system of a multi-phase voltageregulator control system according to some embodiments.

FIG. 4 is a schematic diagram of a multi-phase voltage system accordingto some embodiments.

FIGS. 5A and 5B illustrate schematic drawings of a power circuit for tapchange motors according to some embodiments.

FIG. 6 is a flowchart illustrating a first example process or operationof a multi-phase voltage regulator controller according to someembodiments.

FIG. 7 is a flowchart illustrating a second example process or operationof a multi-phase voltage regulator controller according to someembodiments.

FIG. 8 is a flowchart illustrating a third example process or operationof a multi-phase voltage regulator controller according to someembodiments.

FIG. 9 illustrates an exemplary voltage bandcenter setting according tosome embodiments.

FIG. 10 is a flowchart illustrating a process or operation of reducingvoltage imbalances in a multi-phase voltage regulator control systemaccording to some embodiments.

FIG. 11 illustrates an exemplary interface for configuring a multi-phasevoltage regulator controller.

FIG. 12 a flowchart illustrating a fourth example process or operationof a multi-phase voltage regulator controller according to someembodiments.

FIG. 13 illustrates a block diagram of an exemplary multi-phase voltageregulator controller according to some embodiments.

DETAILED DESCRIPTION

FIGS. 1A-1D illustrate various perspective and frontal views of amulti-phase voltage regulator controller 100 according to one or moreembodiments of the disclosure. Controller 100, for example, may be usedto control the changing of voltage tap positions in a three-phase powersystem. Voltage tap positions may hereinafter be referred to simply as“tap positions.”

As shown, controller 100 includes a front panel 105 that supportsvarious respective control mechanisms, e.g., switches, indicators, etc.,that correspond to three respective phase lines, e.g., phase-A, phase-B,phase-C, of a three-phase power system. In particular, the front panel105 includes a first set of control mechanisms 110A that correspond to afirst regulator used for controlling the regulator tap changer(s)associated with a first phase voltage regulator, e.g., phase-A, of athree-phase power system. The first set of control mechanisms 110A thatcorrespond to a first regulator may hereinafter be referred to as thefirst regulator control 110A. The front panel 105 further includes asecond set of control mechanisms 110B that correspond to a secondregulator used for controlling the regulator tap changer(s) associatedwith a second phase voltage regulator, e.g., phase-B, of a three-phasepower system. Furthermore, the front panel 105 includes a third set ofcontrol mechanisms 110C that correspond to a third regulator used forcontrolling the regulator tap changer(s) associated with third phasevoltage regulator, e.g., phase-C, of a three-phase system. The secondset of control mechanisms 110B that correspond to a second regulator mayhereinafter be referred to as the “second regulator control 110B” andthe third set of control mechanisms 110C that correspond to a thirdregulator may hereinafter be referred to as the “third regulator control110C.” Accordingly, the controller 100 includes regulator controls110A-110C that are used to regulate line voltages of each respectivephase in a three-phase power system by adjusting voltage tap positions.

In accordance with exemplary embodiments, each regulator control110A-110C respectively includes, among other things, several switchesand/or buttons for controlling operation of a respective phase tapchanger for phases A through C of the three-phase power system. Forexample, each regulator control 110A-110C respectively includes a modeswitch 115A-115C used to control whether a respective tap change ismanually controlled or automatically controlled by the controller 100.In addition, each regulator control 110A-110C respectively includespower switches 120A-120C, which are used to control whether a tapchanger, or tap change motor, is powered by an internal or externalpower source. In addition, each regulator control 110A-110C respectivelyincludes a tap change switch 125A-125C used for raising and/or loweringthe positions of a respective voltage tap.

As shown in FIGS. 1C and 1D, the front panel 105 of controller 100further supports one or more additional user-interface components forcontrolling and/or monitoring operation of the regulator tap changer forphases A through C. For example, in some embodiments, the controller 100further includes a display 130 for monitoring various system conditionsand several control buttons 135 for providing various inputs to thecontroller 100. Various indicator lights 140 are also provided forvisually indicating certain conditions, such as forward or reversepower, voltage raise or lower operation, and others. In someembodiments, the front panel 105 includes one or more openings thatprovide access to connection interfaces that provide various modes ofcommunication with controller 100. For example, the controller 100 mayinclude a USB interface 145 and/or smart flash SD card interface 150.Furthermore, in accordance with the exemplary embodiment of FIGS. 1A-1C,the controller 100 may include one or more additional terminal portsthat provide power to the three tap changers, or more specifically themotors for the three tap changers to enable mechanical switching to thenecessary tap(s).

In some embodiments, such as the ones illustrated in FIGS. 1A, 1B, and1D, the regulator controls 110A-110C are arranged vertically along thefront panel 105. That is, with respect to the front panel 105, the firstregulator control 110A is positioned above the second regulator control110B, which is positioned above the third regulator control 110C. Insome embodiments, such as the ones illustrated in FIGS. 1C and 1D, thefront panel 105 is segmented into three sub-panels 160A-160C. Each ofthe three sub-panels 160A-160C corresponds to a respective regulatorcontrol 110A-110C. For example, the first sub-panel 160A, labeled“REGULATOR 1,” includes the first set of control mechanisms 110Aassociated with controlling the voltage regulator of the first phaseline. Similarly, the second sub-panel 160B, labeled “REGULATOR 2,”includes the first set of control mechanisms 110B associated withcontrolling the voltage regulator of the second phase line and the thirdsub-panel 160C, labeled “REGULATOR 3,” includes the third set of controlmechanisms 110C associated with controlling the voltage regulator of thethird phase line. It should be understood that arrangement of theregulators 110A-110C on front panel 105 is not limited to theillustrated embodiments of FIGS. 1A-1D, as the regulator controls110A-110C may be rearranged and/or positioned at various other locationsalong the front panel 105.

Regardless of whether the front panel 105 is segmented into threeseparate sub-panels, each one of the regulator controls 110A-110C iselectrically connected to a single printed circuit board (PCB) withinthe controller 100. That is, all the electrical connections for thecontrol mechanisms included in the regulator controls 110A-110C aresupported by a single PCB. As shown in FIG. 2 , the controller 100includes a first PCB 200 that provides control and/or power to variouscomponents of the controller 100. In particular, the first PCB 200includes respective interfaces, or connections, 205A-205C thatcorrespond to the control mechanisms and/or power connections includedin the regulator controls 110A-110C. Accordingly, the first PCB 200provides all the necessary processing, control signal generation, andpower, for example, to be provided by the regulator controls 110A-110Cto the tap changers, for all three phases of the three-phase powersystem.

The power and control elements of the regulator controls 110A-110C arerelatively high-power analog components. In some embodiments, it ispreferable to separate the high-power analog components supported by afirst board from any additional low power digital components of thecontroller 100. For example, as shown in FIG. 2 , the controller 100 mayfurther include a second PCB 210 that accommodates low-power digitalcomponents and signals. However, it should be noted that in someembodiments, the high-power analog components and signals and thelow-power digital components and signals are accommodated by a singlePCB. Regardless of whether there are one or two boards, according tothis exemplary embodiment similar processing, control, and powergeneration for each of the three phases is maintained entirely on thefirst PCB 200. That is, a separate board or module for each phase, andthus each respective regulator control 110A-110C, is not neededaccording to this embodiment because all processing and power generationfor the tap changers associated with all three phases can be handled onthe first PCB 200.

FIG. 3 illustrates an example block diagram of a control system 300 ofan exemplary tap changing system used for a three-phase power system,according to some embodiments. The control system 300 includes thecontroller 100 which is electrically and/or communicatively connected toa variety of modules or components of the control system 300. Forexample, the controller 100 is connected to the regulator controls110A-110C, a user-interface 305, sensors 310, communication module 315,power supply 320, and tap change motors 325A-325C for adjusting voltagetap positions associated with each respective phase in a three-phasepower system.

As described above, the controller 100 is configured to communicate withthe regulator controls 110A-110C. In particular, the controller 100 maybe configured to receive signals from and/or send signals to theregulator controls 110A-110C when a user operates one or more of themode switches 115A-115C, power switches 120A-120C, and/or tap changeswitches 125A-125C. For example, the controller 100 may be configured toautomatically operate a respective regulator control 110 when thecorresponding mode switch is configured to perform automatic mode ofoperation. Similarly, the controller 100 may be configured to power aparticular regulator control 110 with voltage supplied by the phaselines when the corresponding power switch 120 is moved to the externalpower source setting. Furthermore, when operating in a manual mode ofoperation, the controller 100 may be configured to raise or lower aparticular tap position based on operation of one or more of the tapchange switches 125A-125C.

The controller 100 is further configured to communicate with auser-interface 305 and one or more sensors 310. The user-interface 305includes, for example, the display 130, the control buttons 135, and thevarious indicator lights 140. The sensors 310 may include one or morevoltage sensors used for monitoring the respective voltages of the phaselines, e.g., phases A-C, included in the three-phase power system. Thesensors may also include one or more current sensors, one or moretemperature sensors, one or more additional voltage sensors, and/or oneor more other sensors for monitoring physical and electricalcharacteristics of the tap changing system.

The communication module 315 is configured to provide communicationbetween the controller 100 and one or more external devices (forexample, a smart phone, a tablet, a laptop, etc.) in a three-phase powersystem. In some embodiments, the communication module 315 includes theUSB interface 145 and the smart flash SD card interface 150. In someembodiments, the communication module 315 includes one or more wirelessand/or wired transmitters, receivers, and/or transceivers used forcommunicating with external devices. In some embodiments, thecommunication module 315 is configured to communicate with externaldevices operated by a utility service provider and/or a servicetechnician. In such embodiments, the communication module 315 maycommunicate with the one or more external devices through a network. Thenetwork may be, for example, a wide area network (WAN) (e.g., theInternet, a TCP/IP based network, a cellular network, such as, forexample, a Global System for Mobile Communications [GSM] network, aGeneral Packet Radio Services [GPRS] network, a Code Division MultipleAccess [CDMA] network, an Evolution-Data Optimized [EV-DO] network, anEnhanced Data Rates for GSM Evolution [EDGE] network, a 3 GSM network, a4GSM network, a Digital Enhanced Cordless Telecommunications [DECT]network, a Digital AMPS [IS-136/TDMA] network, or an Integrated DigitalEnhanced Network [iDEN] network, etc.). In other embodiments, thenetwork may be, for example, a local area network (LAN), a neighborhoodarea network (NAN), a home area network (HAN), or personal area network(PAN) employing any of a variety of communications protocols, such asWi-Fi, Bluetooth, ZigBee, etc. In yet another embodiment, the networkincludes one or more of a wide area network (WAN), a local area network(LAN), a neighborhood area network (NAN), a home area network (HAN), orpersonal area network (PAN). In some embodiments, the communicationmodule 315 communicates with one or more peripheral devices in asupervisory control and data acquisition (SCADA) management system.

As shown, the control system 300 of the tap changing system furtherincludes a power supply 320 that is electrically and/or communicativelycoupled to the controller 100 and other components, such as theregulator controls 110A-110C and tap change motors 325A-325C, includedin control system 300. The power supply 320 may be configured toselectively provide power from either an internal power source or anexternal power source to the various components of the control system300. In some embodiments, the power supply 320 includes an internalpower source, such as a rechargeable battery, which may be used toprovide power to one or more components included in the control system300. For example, the power supply 320 may power the control system 300with power from the rechargeable battery when one or more of the powerswitches 120A-120C are set to the internal power source position.

In some embodiments, the power supply 320 is further configured toselectively power components of the control system 300 with powerreceived from an external power source, such as the phase lines includedin a three-phase power system. In such embodiments, the power supply 320may include one or more AC-AC converters, AC-DC converters, and/or DC-DCconverters configured to convert the AC power supplied by phase lines toan appropriate level used for powering the one or more components ofcontrol system 300.

For example, FIG. 4 illustrates an embodiment in which the power supply320 includes converter circuitry that converts power received from athree-phase power system 400 to a level used for powering the controlsystem 300. As shown, the three-phase power system 400 includes a powersource 405, a voltage regulator 410, phase lines 415A-415C, neutral line415N, and ground 420. The power supply 320 includes a converter circuit425 used for converting the AC power transmitted along phase lines415A-415C to a level used for powering the controller 100, the regulatorcontrols 110A-110C, tap change motors 325A-325C, and other components ofthe control system 300. In the illustrated embodiment, the convertercircuit 425 is a three-phase half-wave rectifier that is configured toharvest the positive half-cycles of the AC power transmitted by phaselines 415A-415C and use the harvested power to power the control system300. For example, when one or more of the power switches 120A-120C areset to the external power source position, the controller 100 may beconfigured to power one or more the regulator controls 110A-110C and tapchange motors 325A-325C with the positive half-cycles of AC powertransmitted along the phase lines 415A-415C. In some instances, thepositive half-wave is used for power harvesting. In some instances,other types of converter topologies are used instead of the three-phasehalf-wave rectifier.

Referring again to FIG. 3 , the controller 100 further includes aplurality of electrical and electronic components that provide power,operational control, and protection to the components and modules withinthe controller 100 and/or the control system 300. For example, thecontroller 100 includes, among other things, an electronic processor 330(for example, a microprocessor or another suitable programmable device)and a memory 335. In some embodiments, the electronic processor 330and/or the memory 335 are mounted to a surface of the first PCB 200. Insome embodiments, the electronic processor 330 and/or the memory 335 areembedded within a surface of the first PCB 200. In other embodiments,the electronic processor 330 and/or the memory 335 are otherwiseelectrically and physically coupled to the first PCB 200. In someembodiments, the electronic processor 330 and/or the memory 335 aresupported by the second PCB 210.

The memory 335 includes, for example, a program storage area and a datastorage area. The program storage area and the data storage area caninclude combinations of different types of memory, such as read-onlymemory (ROM) and random-access memory (RAM). Various non-transitorycomputer readable media, for example, magnetic, optical, physical, orelectronic memory may be used. The electronic processor 330 iscommunicatively coupled to the memory 330 and executes softwareinstructions that are stored in the memory 335, or stored in anothernon-transitory computer readable medium such as another memory or adisc. The software may include one or more applications, program data,filters, rules, one or more program modules, and other executableinstructions. In some embodiments, the memory 335 includes one or moremodules configured to perform various functions of controller 100. Forexample, memory 335 may include a voltage comparator module used toanalyze voltages of the phase lines 415A-415C. In some embodiments,memory 335 may additionally or alternatively include a tap change moduleused to generate signals (e.g., raise and/or lower signals) to instructthe tap change motors 325A-325C to change the tap positions based onphase line voltage measurements. In some embodiments, memory 335 mayadditionally or alternatively include a tap change module used togenerate signals (e.g., raise and/or lower signals) to instruct the tapchange motors 325A-325C to change the tap positions based on positionsof the tap change switches 125A-125C.

FIGS. 5A and 5B illustrate an exemplary schematic demonstrating howpower is supplied to each of the tap change motors 325A-325C when thecontroller 100 determines that the voltage of one or more phases, suchas the voltage on one or more of the phase lines 415A-415C, needs to beraised or lowered. As shown, power is provided to the tap change motors325A-325C of each phase even when AC power for any one or more of thephases is de-energized, for example, for maintenance reasons or due to aline failure. It is desired to change the tap positions of each phase,that is, in accordance with the commanded power determined by thecontroller 100 and/or regulator controls 110A-110C, even when one ormore of the phase lines 415A-415C is dead, so the dead phase is set tothe appropriate tap setting when that particular phase is restored.Otherwise, the power distribution system 400 may be unbalanced andoperate inefficiently or exhibit other detrimental properties.

As shown in FIG. 5B, signal Motor-A-BAD, which corresponds to phase-A(e.g., phase line 415A) of a three-phase power system 400, is outputfrom a voltage comparator 505A that compares Motor-A-IN input voltage toa reference voltage, Vref. If the Motor-A-IN input voltage exceeds Vref,the output Motor-A-BAD signal will become low, indicating that there issufficient voltage on the phase line 415A. Thus, under this conditionthe phase-A tap change motor 325A has sufficient power and canfacilitate a tap change. If, to the contrary, the Motor-A-IN inputvoltage does not exceed Vref, the Motor-A-BAD output from the voltagecomparator would be high, indicating there is not enough power on phaseline 415A to power the tap change motor 325A. It is noted, although notexpressly shown in the figures, output signals Motor-B-BAD andMotor-C-BAD, corresponding to phase-B (e.g., phase line 415B) andphase-C (e.g., phase line 415C), are generated in a similar manner asdescribed for signal Motor-A-BAD. As shown in FIG. 5B, the outputvoltage of the comparator is inverted to produce the appropriate logicto match the truth table illustrated in FIG. 5A.

The logic chart below the schematic diagram in FIG. 5A will now bedescribed in accordance with one or more exemplary embodiments. Forexample, according to one possible scenario, if all three phases (e.g.,phase lines 415A-415C) of the three-phase power system 400 havesufficient respective transmission voltages, then, as shown in the lastrow of the logic chart of FIG. 5A, each “Motor IN” signal, i.e.,Motor-A-IN, Motor-B-IN and Motor-C-IN, is at logic “1.” It should benoted that a sufficient transmission voltage need not necessarily be thecorrect voltage pursuant to the present load requirements and ascommanded by the controller 100, but rather a voltage sufficiently highenough to exceed Vref, as described in reference to FIG. 5B.Consequently, because each of the input voltages is high enough, e.g.,non-zero which would indicate an open circuit as would be the case if aparticular phase voltage were offline, the corresponding “Motor BAD”signals, Motor-A-BAD, Motor-B-BAD and Motor-C-BAD, are at logic “0.” Itshould be noted that logic “0” in reference to the Motor BAD signalsmeans that the respective signals are at a low potential. In fact, asdescribed above, when any of the Motor BAD signals are “low,” thisindicates that the respective phase line 415 has sufficient power todrive the corresponding tap change motor 325.

Further, under the circumstances just described where each phase linehas enough voltage, each respective relay 510A-510C shown in FIG. 5A iscontrolled such that the Motor-IN input voltage is delivered to thecorresponding Motor-OUT. For example, the relay 510A in the phase-A pathis controlled such that Motor-A-IN is electrically connected to theMotor-A-OUT signal. Similarly, Motor-B-IN is electrically connected toMotor-B-OUT and Motor-C-IN is connected to Motor-C-OUT. This conditionis illustrated in the logic chart by the MOTOR POWER INPUT columns,Motor-A-IN, Motor-B-IN, Motor-C-IN, having a “1,1,1” condition.Accordingly, the LOGIC OUTPUT columns, Motor-A-BAD, Motor-B-BAD,Motor-C-BAD, have a “0,0,0” condition and the MOTOR POWER OUTPUTcolumns, Motor-A-OUT, Motor-B-OUT, Motor-C-OUT, have an “A, B, C”condition when each respective phase line 415 has sufficient power todrive the corresponding tap change motor 325. Accordingly, power for thetap change motors 325A-325B is provided by each regulator control110A-110C on each individual phase.

If, on the other hand, one of the three phase lines 415A-415C does nothave a sufficient voltage potential (e.g., voltage is less than athreshold for minimum voltage needed to power tap change motor 325),then the corresponding relay circuit 510A-510C is controlled such thatthe tap change motor 325A-325C for that phase is powered by one of theother phase lines that does have sufficient voltage (e.g., voltageexceeds a minimum threshold needed to power the tap change motor 325).For example, phase lines 415A and 415B may have sufficient voltage, butphase line 415C does not have sufficient voltage. This condition isillustrated in the second to last row of the chart and may exist if, forexample, phase line 415C was taken offline or experienced a failure.Under these conditions, tap change motor 325A is supplied with powerfrom phase line 415A, tap change motor 325B is supplied with power fromphase line 415B, and tap change motor 325C is supplied with power fromphase line 415A.

Specifically, the relays 510A-510C shown in FIG. 5A are controlled suchthat Motor-A-IN is electrically connected to the Motor-A-OUT signal andMotor-B-IN is electrically connected to Motor-B-OUT. In this scenario,however, Motor-A-OUT is also connected to Motor-C-OUT, since phase line415C is dead and Motor-C-IN has insufficient voltage to drive the tapchange motor 325C. This condition is illustrated in the logic chart bythe MOTOR POWER INPUT columns, Motor-A-IN, Motor-B-IN, Motor-C-IN,having a “1,1,0” condition. Accordingly, the LOGIC OUTPUT columns,Motor-A-BAD, Motor-B-BAD, Motor-C-BAD, have a “0,0,1” and the MOTORPOWER OUTPUT columns, Motor-A-OUT, Motor-B-OUT, Motor-C-OUT, have an “A,B, A” condition.

Other possible conditions where one or more phase lines 415A-415C areinsufficient to power their respective tap change motors 325A-325C arefurther depicted in the logic chart. That is, it is shown where each ofthe tap change motors 325A-325C for the one or more dead phases wouldreceive power. Furthermore, in some embodiments, the tap change motors325A-325C are not powered solely by the phase line 415A-415C to whichthey are connected. In some embodiments, the tap change motors 325A-325Cmay be powered by the combined rectified positive half-wave cycles ofthe phase lines 415A-415C. In some embodiments, negative half-wavecycles of the phase lines 415A-415C are harvested for powering thesystem instead of or in addition to the negative half-wave cycles.

As described above, when one or more of the mode switches 115A-115C areset to an automatic mode of operation, the controller 100 is configuredto, using the regulator controls 110A-110C, control the tap changemotors 325A-325C to automatically adjust the tap positions. Thecontroller 100 automatically adjusts tap positions to bring the voltageof the three-phase power system 400 within a target band (e.g., within adesired voltage range) of a voltage setpoint, or bandcenter. In someembodiments, the controller 100 is configured implement an “IndependentPhase Independent Operation” control method for controlling the tappositions for each phase line 415A-415C. In such embodiments, thecontroller 100 controls the tap position for a particular phaseaccording to a respective setpoint and compensated voltage associatedwith that particular phase. For example, the controller 100 controls thetap position of phase A based on a phase A voltage setpoint and therespective compensated voltage of phase A. In some embodiments, thecontroller 100 is configured to implement a “Multi-Phase IndependentOperation” control method for controlling the tap positions for eachphase line 415A-415C. In such embodiments, the controller 100 controlsthe tap position for a particular phase according to a multi-phasesetpoint and a respective compensated voltage associated with theparticular phase being adjusted. For example, the controller 100controls the tap position of phase A based on a multi-phase setpoint andthe respective compensated voltage of phase A. The multi-phase setpointmay be, for example, a target bandcenter and/or voltage band for themulti-phase voltage of system 400.

In some embodiments, the controller 100 is configured to regulate thevoltage of the three-phase power system 400 by implementing a “GangedAverage Mode” control method. While implementing the “Ganged AverageMode” control method, the controller 100 controls the tap positions foreach phase line 415A-415C using the same multi-phase setpoint and anaverage compensated voltage of the system 400, which is calculated basedon the respective voltages of all three phases. That is, the controller100 controls, using the regulator controls 110A-110C, the tap positionsfor all three phases based on the same multi-phase setpoint and averagecompensated voltage, not based on individual phase voltage setpoints orcompensated phase voltages that are unique to a particular phase. Byusing the same multi-phase setpoint and average compensated voltage tocontrol the tap positions, the controller 100 effectively moves the tapsthat are positioned at a maximum or minimum setpoint toward a voltagebandcenter to thereby bring the system voltage within a target band.

FIG. 6 is a flowchart illustrating a process, or operation, 600 forregulating system voltage (e.g., controlling tap positions) inaccordance with the “Ganged Average Mode” control method. Althoughillustrated as occurring sequentially, some of the steps may beperformed in parallel. At block 605, the controller 100 determineswhether power flow is in the same direction for all the regulatorcontrols 110A-110C (block 605). If the controller 100 determines thatpower flow is not in the same direction for each of the voltageregulator controls 110A-110C, the controller 100 blocks operation of the“Ganged Average Mode” control method (block 610). In some instances,blocking operation at block 610 includes changing the voltage regulationmethod, by the controller 100, to the “Multi-Phase IndependentOperation” control method to regulate the system voltage.

If the controller 100 determines that power flow is in the samedirection for each of the voltage regulator controls 110A-110C, thecontroller 100 calculates an average compensated voltage of thethree-phase power system 400 (block 615). As described above, theaverage compensated voltage is calculated based on the respectivevoltages of each phase. At block 620, the controller 100 runs a voltageregulation task based on the determined average compensated voltage andthe multi-phase setpoint (block 620). The multi-phase setpoint is usedfor controlling the tap positions for all phases and may include, forexample, a target bandcenter voltage and/or voltage band for thethree-phase power system 400. Running the voltage regulation taskincludes determining whether to issue one of a raise command or a lowercommand based on the average compensated voltage and the multi-phasesetpoint. That is, at block 620, the controller 100 determines a voltageregulation operation, such as issuing a raise command or a lowercommand, based on the average compensated voltage of the system 400 andthe multi-phase setpoint. For example, if the average compensatedvoltage of the system 400 exceeds the multi-phase setpoint, thecontroller 100 might determine to issue a lower command. Likewise, ifthe average compensated voltage of the system 400 is less than themulti-phase setpoint, the controller 100 might determine to issue araise command.

At block 625, the controller 100 determines whether each of theregulator controls 110A-110C are set to the same voltage tap positionbefore issuing the determined command to the regulator controls110A-110C (block 625). If the voltage regulator controls 110A-110C areset to the same tap positions, the controller 100 issues the determinedcommand, such as a raise command or a lower command, to all threevoltage regulator controls 110A-110C (block 630). A raise command issuedto all three voltage regulator controls 110A-110C may be referred to asa “ganged raise command issued” and a lower command issued to all threevoltage regulator controls 110A-110C may be referred to as a “gangedlower command.” A ganged command issued to the regulator controls110A-110C causes each of the tap change motors 325A-325C to be operatedin accordance with the ganged command. After issuing the ganged raisecommand or the ganged lower command to all three voltage regulatorcontrols 110A-110C, the controller 100 continues to regulate the systemvoltage (block 635). For example, the controller 100 repeats the process600 to continue regulating the voltage of the three-phase power system400.

However, if the voltage regulators 110A-110C are not set to the same tapposition at block 625, the controller 100 determines whether theregulation operation determined at block 620 is a raise command (block640). Moreover, the controller 100 evaluates the tap position of eachrespective regulator control 110A-110C in relation to the tap positionof the other two regulator controls 110A-110C before issuing a commandto one or more of the voltage regulator controls 110A-110C (block 640).If the controller 100 determines that the command is a raise command,the controller 100 issues a raise command to the regulator control(s)110A-110C having the lowest tap positions (block 645). However, if thecontroller 100 determines that the command is a lower command, thecontroller 100 issues a lower command to the one or more voltageregulator controls 110A-110C having the highest tap positions (block650). After issuing the lower command(s) at block 645 or 16ssueng theraise command(s) at block 650, the controller 100 continues to regulatethe system voltage (block 635).

In a first example provided with respect to process 600, it will beassumed that at block 640, the controller 100 determines that a raisecommand was issued and that regulator control 110A is set to tapposition 8R, regulator control 110B is set to tap position 8R, andregulator control 110C is set to tap position 6R. In such an example,since the voltage regulator control 110C is set to the lowest tapposition, the controller 100 will issue a raise command to the regulatorcontrol 110C for raising the tap position of phase C (block 645). Afterthe controller 100 increases, using regulator control 110C, the tapposition of phase C from 6R to 7R, the controller 100 then proceeds tocontinue regulating the voltage of system 400 (block 635).

Continuing with this first example, the controller 100 might continueregulating the multi-phase voltage of the distribution system byrestarting the process 600. In this example, performing process 600would again lead to controller 100 arriving at block 640, as the tapsare still at different tap positions (e.g., regulator control 110A isset to tap position 8R, regulator control 110B is set to tap position8R, and regulator 110C is now set to tap position 7R). Thus, if thecontroller 100 determines at block 640 that the issued command isanother raise command, the controller 100 would again issue a raisecommand to the regulator control 110C for raising the tap position ofphase C (block 645). After the controller 100 increases, using theregulator control 110C, the tap position of the phase C from 7R to 8R,the controller 100 then proceeds to continue regulating the multi-phasevoltage of the distribution system 400 (block 635). Continuing with thisfirst example yet again, all three regulator controls 110A-110C are nowset to the same tap position of 8R. Thus, when performing the process600 a third time, the controller 100 would proceed from block 625 toblock 630, at which the controller 100 would issue a ganged command toall three regulator controls 110A-110C. For example, if the controller100 determines at block 620 that another raise command is needed tobring the system voltage within band, the controller 100 would thenissue a ganged raise command to all three regulator controls 110A-110Cat block 630. In operation, the controller 100 may continue to performthe process 600 until the target multi-phase setpoint is satisfied.

As a second example provided with respect to process 600, it will beassumed that at block 640, the controller 100 determines that a raisecommand was issued and that regulator control 110A is set to tapposition 6R, regulator control 110B is set to tap position 7R, andregulator control 110C is set to tap position 8R, the controller 100. Insuch an example, since the regulator control 110A is set to the lowesttap position, the controller 100 will issue a raise command to theregulator control 110A for raising the tap position of phase A (block645). After the controller 100 increases, using regulator control 110A,the tap position of the phase A from 6R to 7R, the controller 100 thenproceeds to continue regulating the multi-phase voltage of the system400 (block 635).

Continuing with this second example, the controller 100 might continueregulating the multi-phase voltage of the distribution system byrestarting the process 600. In this example, performing process 600again would lead to controller 100 arriving at block 640, as the tapsare still at different tap positions (e.g., regulator control 110A isnow set to tap position 7R, regulator control 110B is set to tapposition 7R, and regulator control 110C is set to tap position 8R).Thus, if the controller 100 determines at block 640 that the issuedcommand is another raise command, the controller 100 would then issueraise commands to the regulator controls 110A, 110B for respectivelyraising the tap positions of phases A, B. After the controller 100increases the tap positions of the phases A, B from 7R to 8R, thecontroller 100 then proceeds to continue regulating the multi-phasevoltage of the system 400 (block 635). Continuing with this secondexample yet again, all three regulator controls 110A-110C are now set tothe same tap position of 8R. Thus, when performing the process 600 athird time, the controller 100 would proceed from block 625 to block630, at which the controller 100 would issue a ganged command to allthree regulator controls 110A-110C. For example, if the controller 100determines at block 620 that another raise command is needed at to bringthe system voltage within band, the controller 100 would then issue aganged raise command to all three regulator controls 110A-110C at block630. Although the first and second examples are described with respectto raise commands, similar logic could be applied to scenarios in whichlower commands are issued to bring the system voltage within band.

While performing process 600, each individual phase might also becontrolled in accordance with voltage setpoint limits and settings thatare determined in accordance with phase voltage and currentmeasurements. The setpoint limits may include, for example, user-definedvoltage band thresholds and tap position settings. In some cases, a tapposition increase or decrease command issued for a particular phase(e.g., phase A) may violate the settings used to govern operation ofprocess 600. In such cases, the controller 100 is configured to stopcontrolling non-violated phases (e.g., phases B and C) with the “GangedAverage Mode” control method and, instead, begin controlling thenon-violated phases using individual phase measurements until theblocking condition is no longer present. Before restoring the “GangedAverage Mode” control method of controlling the tap positions of phasesA-C, a 1V hysteresis may be applied.

In some embodiments, the controller 100 is configured to regulate thevoltage of the three-phase power system 400 by implementing a “GangedControlling Phase Mode” control method. The “Ganged Controlling PhaseMode” control method is similar to the “Ganged Average Mode” controlmethod described above. However, while implementing the “GangedControlling Phase Mode” control method, the controller 100 is configuredto set a controlling phase (e.g. phase A) that is used to control all ofthe regulator controls 110A-110C instead of using an average compensatedvoltage for controlling regulator controls 110A-110C. Accordingly, thecontrolling phase is used to set the voltage regulation operation (e.g.,determine raise or lower command). Thus, if one of the non-controllingphases experiences a change in regulation direction (e.g., raise orlower), either from a power flow change or auto-determination change,the non-controlling phase would still be regulated in the direction ofthe controlling phase.

FIG. 7 is a flowchart illustrating a process, or operation, 700 forregulating system voltage (e.g., controlling tap positions) inaccordance with the “Ganged Controlling Phase Mode” control method.Although illustrated as occurring sequentially, some of the steps may beperformed in parallel. At block 705, the controller 100 designates thecontrolling phase that will be used to set the voltage regulationoperation (block 705). This includes determining the designated phasecompensated voltage based on the compensated voltage of the designatedcontrolling phase. In some examples, the controller 100 determinesadditional values, such as averages and setpoints, associated with thedesignated controlling phase. At block 710, the controller 100 beginsregulating the three-phase voltage system 400 based on the values of thedesignated controlling phase voltage and designated setpoints (block710). For example, this includes determining, by the controller 100, avoltage regulation operation based on the designated controlling phasevoltage and designated setpoints. As described above with respect toprocess 600, a voltage regulation operation may be, for example, a raisecommand or a lower command.

At block 715, the controller 100 determines whether each of the voltageregulators 110A-110C are set to the same tap position before issuing thedetermined command to the regulator controls 110A-110C (block 715). Ifthe regulator controls 110A-110C are set to the same tap positions, thecontroller 100 issues a ganged command, such as a ganged raise commandor a ganged lower command, to all three regulator controls 110A-110C(block 720). After issuing the ganged command to all three regulatorcontrols 110A-110C, the controller 100 continues to regulate the systemvoltage (block 725). For example, the controller 100 repeats the process600 to continue regulating the voltage of the three-phase power system400.

However, if the regulator controls 110A-110C are not set to the same tapposition at block 715, the controller 100 determines whether theregulation operation determined at block 710 is a raise command (block730). Moreover, the controller 100 evaluates the tap position of eachrespective regulator control 110A-110C in relation to the tap positionof the other two regulator controls 110A-110C before issuing a commandto one or more of the regulator controls 110A-110C (block 730). If thecontroller 100 determines that the command is a raise command, thecontroller 100 issues a raise command to the regulator control(s)110A-110C having the lowest tap positions (block 735). After issuing theraise command(s), the controller 100 continues to regulate the systemvoltage (block 725). However, if the controller 100 determines that thecommand is a lower command, the controller 100 issues a lower command tothe one or more regulator controls 110A-110C having the highest tappositions (block 740). After issuing the lower command(s), thecontroller 100 continues to regulate the system voltage (block 725).

In some embodiments, the controller 100 is configured to regulate thevoltage of system 400 by implementing a “Multi-Phase Average” controlmethod. Similar to the “Ganged Average Mode” control method, whileimplementing the “Multi-Phase Average” control method, the controller100 controls the tap positions for each phase line 415A-415C using thesame multi-phase setpoint and an average compensated voltage of thesystem 400. However, when the controller 100 implements the “Multi-PhaseAverage” control method, control is limited to the phase most out ofband of the desired voltage range. That is, unlike the “Ganged AverageMode” control method, the controller 100 does not issue ganged raisecommand or ganged lower commands to all regulator controls 110A-110C atonce. If any of the regulator controls 110A-110C is blocked whileimplementing the “Multi-Phase Average” control method, the controller100 will switch from using the “Multi-Phase Average” control method tousing the “Multi-Phase Independent Operation” control method forcontrolling the tap positions.

FIG. 8 is a flowchart illustrating a process, or operation, 800 forregulating system voltage (e.g., controlling tap positions) inaccordance with the “Multi-Phase Average” control method. Althoughillustrated as occurring sequentially, some of the steps may beperformed in parallel. At block 805, the controller 100 determineswhether operation of any of the regulator controls 110A-110C is blocked(block 805). If operation of one or more of the regulator controls110A-110C is blocked, the controller 100 begins using the “Multi-PhaseIndependent Operation” control method for regulating the system voltage(block 810). If none of the regulator controls 110A-110C are blockedfrom operation, the controller 100 calculates an average compensatedvoltage of the three-phase power system 400 (block 815). As describedabove, the average compensated voltage is calculated based on therespective voltages of each phase.

At block 820, the controller 100 runs a voltage regulation task based onthe determined average compensated voltage and the multi-phase setpoint(block 820). Running the voltage regulation task includes determiningwhether to issue one of a raise command or a lower command based on theaverage compensated voltage and the multi-phase setpoint. That is, atblock 820, the controller 100 determines a voltage regulation operation,such as issuing a raise command or a lower command, based on the averagecompensated voltage and multi-phase setpoint that will bring the voltageof the distribution system 400 within band.

At block 825, the controller 100 determines whether the regulationoperation determined at block 820 is a raise command (block 825).Moreover, the controller 100 evaluates the respective voltage of eachphase in relation to the voltage of the other two phase before issuing acommand to one or more of the regulator controls 110A-110C (block 825).If the controller 100 determines that the command is a raise command,the controller 100 issues a raise command to the voltage regulator110A-110C associated with the phase having the minimum, or lowest,voltage (block 830). After issuing the raise command, the controller 100continues to regulate the system voltage (block 835). If the controller100 determines that the command is a lower command, the controller 100issues a lower command to the regulator control 110A-110C associatedwith the phase having the maximum, or highest, voltage (block 840).After issuing the lower command, the controller 100 continues toregulate the system voltage (block 835).

As described above, the controller 100 uses the regulator controls110A-110C to adjust the positions of respective taps based on thevoltages of phase lines 415A-415C relative to a voltage bandcenter. Forexample, when the three-phase voltage of a power system, suchthree-phase power system 400, decreases below a predefined voltage levelthat is less than the voltage bandcenter, the controller 100 may beconfigured to raise, using the regulator controls 110A-110C and the tapchange motors 325A-325C, one or more of the voltage tap positions to apoint of higher voltage. This has the effect of increasing the systemvoltage. Similarly, as another example, when the voltage of a powersystem increases above a predefined voltage level that is greater thanthe voltage bandcenter, the controller 100 may be configured to lower,using the regulator controls 110A-110C and the tap change motors325A-325C, one or more of the tap positions to a point of lower voltage.This has the effect of lowering the system voltage.

The regulator controls 110A-110C, which respectively correspond to phaselines 415A-415C, are generally configured to operate in accordance withthe same bandcenter voltage and bandwidth settings. For example, asshown in FIG. 9 , the voltage regulator controls 110A-110C may beconfigured to operate in accordance with a bandcenter voltage of 120 V(normalized with voltage transformer secondary voltage) and a bandwidthof 3 V. For induction motor loads, NEMA MG1 provides guidance on thetemperature increase of the motor for unbalance voltage supply voltages,as even small voltage imbalances can result in large current imbalancesflowing through the phase lines 415A-415C. For example, a voltageimbalance of 3.5% across phase lines 415A-415C can may result 25%temperature increases in large loads, such as polyphase inductionmotors.

Various methods, such as the ganged and independent control methodsdescribed herein, for regulating system voltage may be used to reducevoltage imbalances occurring within the three-phase power system 400.However, some voltage regulation methods used for controlling the tappositions are ineffective in accounting for a source voltage imbalancethat requires the regulator controls 110A-110C to be at different tappositions to obtain balanced three-phase voltages. Also, if the load oneach phase line 415A-415C is not balanced and the line drop compensationis used to calculate the load voltage down the feeder using the loadcurrent measurement and the line impedance, the regulator controls110A-110C should be at different taps to obtain balanced voltages. Thismay be difficult when a voltage regulation method that sets therespective phase taps to the same positions is used.

Accordingly, another method for regulating system voltage by controllingthe tap positions, as described below, is proposed to reduce theimbalance in voltage supplied to three-phase loads on the system 400.FIG. 10 is a flowchart illustrating a process, or operation, 1000 forreducing the imbalance in voltage supplied to three-phase loads in powersystem 400. It should be understood that although illustrated asoccurring sequentially, some of the steps may be performed in parallel.

The controller 100 determines whether all three phase lines 415A-415Chave a voltage that are within a band of the bandcenter voltage (block1005). For example, with reference to the example illustrated in FIG. 9, the controller 100 determines whether the phase lines 415A-415C are atvoltages within a 3 V band centered at 120 V. When one or more of thephase line voltages are not within a band of the bandcenter voltage, thecontroller 100 performs an operation to bring the out-of-band phasewithin a band of the bandcenter voltage (block 1010). For example, thecontroller 100 may use one or more of the voltage regulation methodsdescribed above (e.g., “Ganged Average Mode,” “Ganged Controlling PhaseMode,” “Multi-Phase Average,” etc.) to bring the out-of-band phasewithin a band of the bandcenter.

When all three of the phase line voltages are within a band of thebandcenter voltage, the controller 100 determines whether any voltagedifference between the phases (e.g., voltage difference between phaseline 415A and 415B, voltage difference between phase line 415A and 415C,and voltage difference between phase line 415B and 415C) exceed aminimize phase voltage differential (MPVD) threshold value (block 1015).For example, as shown in FIG. 11 , which illustrates an exemplaryinterface for configuring the controller 100, the controller 100 may beconfigured to operate in accordance with an MPVD threshold value equalto 0.5 V. However, it should be understood that other values for theMPVD may be chosen instead.

When a voltage difference between two or more of the phase lines415A-415C exceeds the MPVD, the controller 100 is configured to reducethe voltage differential by moving the respective voltage tap, using aregulator control 110 and voltage tap motor 325, associated with thephase line 415 that has a voltage furthest from the bandcenter voltage(block 1020). For example, with reference to FIG. 9 , the voltage of thefirst phase line 415A and the voltage of the second phase line 415B bothdiffer from the bandcenter voltage by approximately 1.5 V. Inparticular, the voltage of the first phase line 415A is 1.5 V greaterthan the bandcenter voltage and the voltage of the second phase line415B is 1.5 V less than the bandcenter voltage. Accordingly, thecontroller 100 controls the regulator control 110A to lower the tapposition associated with phase line 415A. Similarly, the controller 100controls the regulator control 110B to raise the tap position associatedwith phase line 415B. In some embodiments, the voltage tap positions arenot moved until the completion of a set time delay. The controller 100may continue to perform process 1000 until none of the voltagedifferences between the phases (e.g., voltage difference between phaseline 415A and 415B, voltage difference between phase line 415A and 415C,and voltage difference between phase line 415B and 415C) exceed the MPVDthreshold value.

In an alternative embodiment of the method for reducing the imbalance involtage supplied to three-phase loads, the controller 100 may beconfigured to calculate the respective voltage difference between eachphase line 415A-415C and the bandcenter voltage instead of calculatingvoltage differences between the phase lines 415A-415C. For example, thecontroller 100 may be configured to calculate the voltage differencebetween phase line 415A and the bandcenter voltage, the voltagedifference between phase line 415B and the bandcenter voltage, and thevoltage difference between phase line 415C and the bandcenter voltage.In such embodiments, the controller 100 then compares the voltagedifferences between phase lines 415A-415C and the bandcenter voltage tothe MPVD threshold before raising or lower voltage tap positions.

FIG. 12 is flowchart that illustrates another example method, orprocess, 1200 for regulating voltage of a three-phase power system, suchas the three-phase power system 400. It should be understood thatalthough illustrated as occurring sequentially, some of the steps may beperformed in parallel.

At block 1205, the controller 100 starts the process 1200 (block 1205).At block 1210, the controller 100 determines whether a target clockcycle condition, for example a clock cycle tick of 260.4 microseconds,is met (block 1210). If the target clock cycle condition is met, thecontroller 100 performs an interrupt driven service routine (blocks1215-1225). At block 1215, the controller 100 samples each analogchannel feed, and correspondingly, converts the sampled analog signalsto digital signals (block 1215). At block 1220, the controller 100applies a recursive discrete fourier transform (DFT) to each channelfeed input (block 1220). At block 1225, the controller 100 calculatesthe current flowing through the tap change motors 325A-325C (block1225).

At block 1230, the controller 100 determines whether a target number ofsamples, such as 64 samples, have been counted (block 1230). If thetarget number of samples have not been counted, the controller 100returns to block 1210. If the target number of samples have beencounted, the controller 100 performs a status update for one or more ofthe tap change motors 325A-325C (block 1235). Performing the statusupdate might include checking the value(s) of the current flowingthrough one or more of the tap change motors 325A-325C.

At block 1240, the controller 100 determines whether the state of one ormore of the tap change motors 325A-325C is equal to zero (block 1240).If, at block 1240, the controller 100 determines that the state of oneor more of the tap change motors 325A-325C is zero, the controller 100performs a first routine to manage the voltage setpoints of the systemand manage the status of electrically erasable programmable read-onlymemory (EEPROM) coupled to controller 100 (block 1245). After block1245, the controller 100 increments the state of the one or more tapchange motors 325A-325C by one (block 1250) and determines whether theupdated state of the one or more tap change motors 325A-325C is greaterthan three (block 1255). If the state of one or more of the tap changemotors 325A-325C is greater than three, the controller 100 sets thestate of the one or more tap change motors 325A-325C to zero (block1260) before returning to block 1235. If the state of one or more of thetap change motors 325A-325C is not greater than three, the controller100 returns to block 1235.

Referring back to block 1240, if the controller 100 determines that thestate of one or more of the tap change motors 325A-325C is not equal tozero, the controller 100 determines whether the state of one or more ofthe tap change motors 325A-325C is equal to one (block 1265). If, atblock 1265, the controller 100 determines that the state of one or moreof the tap change motors 325A-325C is equal to one, the controller 100performs one or more housekeeping tasks (block 1270) and proceeds toblock 1250. If, at block 1265, the controller 100 determines that thestate of one or more of the tap change motors 325A-325C is not equal toone, the controller 100 determines whether the state of one or more ofthe tap change motors 325A-325C is equal to two (block 1275).

If, at block 1275, the controller 100 determines that the state of oneor more of the tap change motors 325A-325C is equal to two, thecontroller 100 performs one or more datalogging tasks (block 1280) andproceeds to block 1250. If, at block 1275, the controller 100 determinesthat the state of one or more of the tap change motors 325A-325C is notequal to two, the controller 100 determines whether the state of one ormore of the tap change motors 325A-325C is equal to three (block 1285).

If, at block 1285, the controller 100 determines that the state of oneor more of the tap change motors 325A-325C is equal to three, thecontroller 100 performs one or more voltage regulation routines for eachphase (block 1290). For example, the controller 100 uses one or more ofthe voltage regulation methods described herein to regulate the voltage.After regulating the phase voltages, the controller 100 proceeds toblock 1250. If, at block 1285, the controller 100 determines that thestate of one or more of the tap change motors 325A-325C is not equal tothree, the controller 100 outputs an error notification (block 1295)before proceeding to block 1260.

FIG. 13 illustrates a block diagram 1300 of an example hardwarearchitecture that may be used to implement one or more of the voltageregulation methods described herein. It should be understood that thehardware architecture illustrated in FIG. 13 is provided merely as anexample and is not intended to limit the scope of the multi-phasevoltage regulation methods described herein in any way. As shown, thehardware architecture includes a computing module having a processor(CPU) that is coupled to a secure flash bootloader, secure dynamicrandom access memory (SDRAM), and static random access memory (SRAM).The computing module is connected to additional storage componentsincluding an external storage card, data storage, and program flashstorage.

The hardware architecture further includes a power supply and variouscommunication components that are connected to the computing module. Forexample, the communication components include first and second universalasynchronous receiver-transmitters (UART), an ethernet port, and auniversal serial bus (USB). Furthermore, the hardware architectureincludes an ADC for converting analog inputs to the computing module,EEPROM for storing current settings of the system, and a digitalinput/output interface.

In the foregoing specification, specific examples, features, and aspectshave been described. However, one of ordinary skill in the artappreciates that various modifications and changes can be made withoutdeparting from the scope of the invention as set forth in the claimsbelow. Accordingly, the specification and figures are to be regarded inan illustrative rather than a restrictive sense, and all suchmodifications are intended to be included within the scope of presentteachings.

The benefits, advantages, solutions to problems, and any element(s) thatmay cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. The invention is definedsolely by the appended claims including any amendments made during thependency of this application and all equivalents of those claims asissued.

Moreover in this document, relational terms such as first and second,top and bottom, and the like may be used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions. The terms “comprises,” “comprising,” “has,”“having,” “includes,” “including,” “contains,” “containing” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises, has,includes, contains a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus. An element proceeded by“comprises . . . a,” “has . . . a,” “includes . . . a,” or “contains . .. a” does not, without more constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises, has, includes, contains the element. The terms“a” and “an” are defined as one or more unless explicitly statedotherwise herein. The terms “substantially,” “essentially,”“approximately,” “about” or any other version thereof, are defined asbeing close to as understood by one of ordinary skill in the art, and inone non-limiting embodiment the term is defined to be within 10%, inanother embodiment within 5%, in another embodiment within 1% and inanother embodiment within 0.5%. The term “coupled” as used herein isdefined as connected, although not necessarily directly and notnecessarily mechanically. A device or structure that is “configured” ina certain way is configured in at least that way, but may also beconfigured in ways that are not listed.

It will be appreciated that some embodiments may be comprised of one ormore generic or specialized processors (or “processing devices”) such asmicroprocessors, digital signal processors, customized processors andfield programmable gate arrays (FPGAs) and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethod and/or apparatus described herein. Alternatively, some or allfunctions could be implemented by a state machine that has no storedprogram instructions, or in one or more application specific integratedcircuits (ASICs), in which each function or some combinations of certainof the functions are implemented as custom logic. Of course, acombination of the two approaches could be used.

Moreover, an embodiment can be implemented as a computer-readablestorage medium having computer readable code stored thereon forprogramming a computer (e.g., comprising a processor) to perform amethod as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, a CD-ROM, an optical storage device, a magnetic storagedevice, a ROM (Read Only Memory), a PROM (Programmable Read OnlyMemory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory) and a Flashmemory. Further, it is expected that one of ordinary skill,notwithstanding possibly significant effort and many design choicesmotivated by, for example, available time, current technology, andeconomic considerations, when guided by the concepts and principlesdisclosed herein will be readily capable of generating such softwareinstructions and programs and ICs with minimal experimentation.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus, the following claimsare hereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

What is claimed is:
 1. A control system for a multi-phase power systemincluding a first phase line, a second phase line, and a third phaseline, the control system comprising: a first regulator controlconfigured to control a first tap changer; a second regulator controlconfigured to control a second tap changer; a third regulator controlconfigured to control a third tap changer, each of the first tapchanger, the second tap changer, and the third tap changer associatedwith a respective phase line; a converter circuit configured to convertpower flowing through the first, second, and third phase lines to levelsused for powering the first, second, and third tap changers; and anelectronic processor coupled to the first regulator control, the secondregulator control, and the third regulator control, the electronicprocessor configured to: determine whether a voltage level of the firstphase line exceeds a threshold; control a first relay to power the firsttap changer with power converted from the first phase line to affect atap change on the first phase line when the voltage level of the firstphase line exceeds the threshold; and control a second relay to powerthe first tap changer with power converted from the second phase line toaffect a tap change on the first phase line when the voltage of thefirst phase line does not exceed the threshold.
 2. The control system ofclaim 1, wherein the electronic processor is further configured to:determine whether a voltage level of the second phase line exceeds thethreshold when the voltage level of the first phase line does not exceedthe threshold; determine whether a voltage level of the third phase lineexceeds the threshold when the voltage level of the second phase linedoes not exceed the threshold; and control a third relay to power thefirst tap changer with power converted from the third phase line toaffect a tap change on the first phase line when the voltage of thefirst phase line does not exceed the threshold, the voltage of thesecond phase line does not exceed the threshold, and the voltage of thethird phase line exceeds the threshold.
 3. The control system of claim2, wherein the electronic processor is further configured to: controlthe third relay to power the second tap changer with power convertedfrom the third phase line to affect a tap change on the second phaseline when the voltage of the second phase line does not exceed thethreshold and the voltage of the third phase line exceeds the threshold.4. The control system of claim 3, wherein the electronic processor isfurther configured to: control the third relay to power the third tapchanger with power converted from the third phase line to affect a tapchange on the third phase line when voltage of the third phase lineexceeds the threshold.
 5. The control system of claim 1, wherein theconverter circuit harvests positive half cycles of the power flowingthrough the first, second, and third phase lines to power the first,second, and third tap changers.
 6. The control system of claim 1,wherein the first regulator control, the second regulator control, andthe third regulator control are supported on a single printed circuitboard (PCB) that is coupled to the electronic processor.
 7. The controlsystem of claim 1, further comprising a front panel including: a firstsub-panel associated with first regulator control; a second sub-panelassociated with the second regulator control; and a third sub-panassociated with the third regulator control.
 8. A control system for amulti-phase power system including a first phase line, a second phaseline, and a third phase line, the control system comprising: a firstregulator control configured to control a first tap changer; a secondregulator control configured to control a second tap changer; a thirdregulator control configured to control a third tap changer, each of thefirst tap changer, the second tap changer, and the third tap changerassociated with a respective phase line; and an electronic processorcoupled to the first regulator control, the second regulator control,and the third regulator control, the electronic processor configured to,determine an average voltage of the multi-phase power system based on avoltage of the first phase line, a voltage of the second phase line, anda voltage of the third phase line; determine a voltage regulationcommand based on the average voltage and a multi-phase setpoint;determine whether the first tap changer, the second tap changer, and thethird tap changer are set to a same tap position; issue the voltageregulation command to the first regulator control when the first tapchanger, the second tap changer, and the third tap changer are at thesame tap position.
 9. The control system of claim 8, wherein theelectronic processor is further configured to: determine whether thevoltage regulation command is a raise command or a lower command;determine which of the first tap changer, the second tap changer, andthe third tap changer is set to a lowest tap position; and issue thevoltage regulation command to the regulator control associated with therespective tap changer that is set to the lowest tap position when thevoltage regulation command is a raise command.
 10. The control system ofclaim 8, wherein the electronic processor is further configured to:determine whether the voltage regulation command is a raise command or alower command; determine which of the first tap changer, the second tapchanger, and the third tap changer is set to a highest tap position; andissue the voltage regulation command to the regulator control associatedwith the respective tap changer that is set to the highest tap positionwhen the voltage regulation command is a lower command.
 11. The controlsystem of claim 8, wherein the multi-phase setpoint includes a targetbandcenter voltage for the multi-phase power system.
 12. The controlsystem of claim 11, wherein the electronic processor is furtherconfigured to: determine whether the average voltage exceeds the targetbandcenter voltage by a first amount; and wherein the voltage regulationcommand is a lower command when the average voltage exceeds targetbandcenter voltage by the first amount.
 13. The control system of claim11, wherein the electronic processor is further configured to: determinewhether the average voltage does not exceed the target bandcentervoltage by a first amount; and wherein the voltage regulation command isa raise command when the average voltage does not exceed the targetbandcenter voltage by the first amount.
 14. The control system of claim8, wherein the electronic processor is further configured toindependently control each of the first, second, and third regulatorcontrols when operation of at least one of the first, second, and thirdregulator controls is blocked.
 15. A control system for a multi-phasepower system including a first phase line, a second phase line, and athird phase line, the control system comprising: a first regulatorcontrol configured to control a first tap changer; a second regulatorcontrol configured to control a second tap changer; a third regulatorcontrol configured to control a third tap changer, each of the first tapchanger, the second tap changer, and the third tap changer associatedwith a respective phase line; and an electronic processor coupled to thefirst regulator control, the second regulator control, and the thirdregulator control, the electronic processor configured to, determinewhether each of a voltage of the first phase line, a voltage of thesecond phase line, and a voltage of the third phase line are within bandof a target bandcenter; perform a voltage regulation operation when oneor more of the voltages of the first phase line, the second phase line,and the third phase line are out of band of the target bandcenter; andadjust a tap position of the tap changer associated with the phase linehaving a voltage furthest from the bandcenter.
 16. The control system ofclaim 15, wherein the electronic processor is further configured to:determine whether any of the voltages of the first phase line, thesecond phase line, and the third phase line differ from the targetbandcenter by more than a threshold; and adjust the tap position of thetap changer associated with the phase line having a voltage furthestfrom the bandcenter when of the voltages of the first phase line, thesecond phase line, and the third phase line differ from the targetbandcenter by more than the threshold.
 17. The control system of claim15, further comprising a front panel including: a first sub-panelassociated with first regulator control; a second sub-panel associatedwith the second regulator control; and a third sub-pan associated withthe third regulator control.
 18. The control system of claim 15, whereinthe voltage regulation operation includes controlling the first, second,and third tap changers in a ganged manner.
 19. The control system ofclaim 15, wherein the voltage regulation operation includes controllingthe first, second, and third tap changers in an independent manner. 20.The control system of claim 15, wherein a value of the threshold can bedefined by a user.